“Shareholder activism is an important mechanism for imposing market discipline on the decisions of corporate executives and directors, and union pension funds take an active role in this process,” the authors state. “Are union-sponsored proposals made solely in the interest of their pension beneficiaries? Or are they used to further social and political priorities that are important to union leadership?”

Between 2004 and 2011, the paper notes, the union group filed six proposals at Comcast, a company targeted by the International Brotherhood of Electrical Workers. “Similarly, the AFL-CIO filed 11 proposals at largely non-union Wal-Mart and Target, while filing only three at unionized grocery store chains Safeway and Kroger.”

Furthermore, Larcker and Tayan go on to point out that the AFL-CIO’s proposals are generally not supported by other shareholders. “For example, a proposal that companies advocate on behalf of US healthcare reform in 2009 received only 5.5 percent support among the 18 companies where the proposal was filed.”

(Of course, the AFL-CIO’s proposals may be unpopular among other shareholders without running counter to union members’ best interests.)

Union pension funds are not the only institutional investors who may get active on behalf of more than increased returns.

Earlier this month, New Zealand’s $17 billion sovereign wealth fund excluded three companies from its portfolio for their roles in the Israel-Palestine conflict. The fund passively held shares in firms that transgressed its relatively strict responsible investing policy due to “their involvement in constructing Israeli settlements…and a separation barrier in the Occupied Palestinian Territories.”